Heat treating furnace



y 1957 H. N. IPSEN 2,800,317

HEAT TREATING FURNACE Filed Oct. 19,1955

T0 may United States Patent ()fiice Pa n ed July .3,, 957

HEAT TREATING FURNACE Harold N. Ipsen, Rockford, Ill.

Application October 19, 1953, Serial No. 386,834

1 Claim. (Cl. 263-2) This invention relates to heat treating furnacesand has particular reference to a furnace in which the atmosphere withinthe furnace chamber is circulated by a fan mounted on the inner end of ashaft projecting through one wall of the furnace. In furnaces of thistype, the shaft, which is driven by a motor disposed outside thefurnace, is journaled exteriorly of the furnace wall and is cooled by awater jacket to prevent overheating of the bearings.

One object of the invention is to provide a furnace of the abovecharacter with a new and improved water jacket which insures that thefan shaft is uniformly cooled, which prevents the shaft from becomingdistorted both when the shaft is idle and when it is turning, and whichmaintains the shaft concentric with the bore of the water jacket withoutthe necessity of a special and complicated construction.

Other objects and advantages of the invention will become apparent fromthe following detailed description taken in connection with theaccompanying drawing, in which the single figure is a transversesectional view of a furnace with a water jacket embodying the novelfeatures of the present invention.

As shown in the drawing for the purpose of illustration, the inventionis embodied in a heat treating furnaoe whose top, bottom and side walls11, 12 and 13 define a chamber 14 in which workpieces (not shown) areplaced for treatment. In furnaces of this type, the workpieces aredisposed within a box-like baffle 15 which rests on blocks 16 on thebottom wall 12 of the furnace and is spaced from the furnace walls. Toheat the chamber 14, heating elements such as vertical gas burner tubes17 are disposed between the side walls of the baffle 15 and the furnaceside walls 13 and extend between the top and bottom walls 11 and 12 ofthe furnace, the tubes being secured to these walls.

In order that the workpieces within the baffie 15 are heated uniformly,the atmosphere in the chamber 14 is circulated about the workpieces by afan 18 which directs the atmosphere laterally over the top of thebaffie, then down between the side walls 13 and the sides of the bafileacross the heating tubes 17, up into the inside of the baffle throughholes 19 in the baffle hearth 20, and finally back to the fan through acentral hole 21 in the arch 22 of the baffle. The fan 18 is mounted onthe lower end of a vertical shaft 23 projecting down through a hole 24in the top wall 11 of the furnace and connected to the shaft 25 of amotor 26 which is secured to the top of the furnace.

Herein, the motor shaft 25 is hollow and its bore 27 is flared at thelower end to receive the tapered upper end portion 28 of the fan shaft23. The latter is held rigidly on the motor shaft by a draw bolt 29projecting down through the motor shaft and threaded into the fan shaft.Thus, by tightening the bolt, the fan shaft is drawn into the flaredportion of the motor shaft so that, in effect, the fan shaft becomes arigid extension of the motor shaft. Within the casing of the motor, thehollow shaft 25 is journaled in spaced bearings 30 and 31 dis posed atopposite ends of the motor and mounted in the motor casing. In orderthat the fan and motor shafts 23 and 25 as well as the bearings 30 and31 do not become overheated, a water jacket 32 seated in the top wall 11of the furnace encircles and cools the fan shaft.

In accordance with the present invention, the water jacket 32 isconstructed in a novel manner to insure effective and uniform cooling ofthe fan shaft 23 while holding the shaft out of running contact with thejacket.

For this purpose, the shaft 23 is journaled on the water' jacket so thatit is maintained in true coaxial relationship with the jacket. In thisway, only a small clearance between the shaft and the water jacket isrequired permitting the latter to dissipate the heat from the shaftquickly and effectively while, at the same time, the spacing between theshaft and the jacket is maintained precisely the same around the entireperiphery of the shaft which thus is uniformly cooled and prevented frombecoming distorted.

In the present instance, the water jacket 32 is in the form of a tubularmember which is flanged at its upper end as indicated at 33 to seat inthe outer side of the top wall 11 of the furnace coaxially with the hole24 and extend in along the fan shaft 23. The shaft projects down throughthe cylindrical bore 34 of the jacket which is hollow and thus providesan annular cavity 35 encircling the fan shaft. Coolant, such as water,is admitted to the cavity through an inlet pipe 36 threaded into thetubular jacket and flows around the shaft 23 and out through a secondpipe 37. The coolant carries away the heat from the surface of thejacket bore 34 and thus cools the shaft 23.

To maintain the fan shaft 23 concentric with the bore 34 of the waterjacket 32, the shaft is journaled directly on the water jacket. To thisend the casing of the motor 26 is rigid with and may, as shown in thedrawing, be cast integrally with the jacket. Thus, the bearings 30 and31, which in effect are mounted on the water jacket, are fixed relativeto the bore 34. Since the bearings and the bore bear a constantrelationship, the fan shaft 23 is held exactly concentric with the bore.

By journaling the fan shaft 23 directly on the water jacket 32, only avery small spacing between the shaft and the wall of the bore 34 isrequired. This spacing may be on the order of .005 of an inch whilemaintaining the shaft concentric with the bore so that the shaft is outof running contact with the water jacket at all times. Such closespacing allows the water to cool the fan shaft effectively since littleof the cooling effect is lost between the shaft and the wall of the bore34. At the same time, there is no danger of the shaft binding in thebore. Because the shaft is precisely concentric with the bore wall, thespacing between the two is, for all practical purposes, exactly the sameall around the shaft. As a result, the cooling effect of the waterjacket is the same at all points around the shaft. Hence, no part of theshaft is cooler than another even when the shaft is not turning and,therefore, the likelihood of warping or distortion of the shaft due touneven heating is substantially eliminated.

I claim as my invention:

A furnace having, in combination, a walled enclosure defining a heatedchamber, one of the walls of said enclosure having a hole therethroughand opening into said chamber, a tubular member seated in said Wall onthe out er side of said enclosure and having a bore coaxial with saidhole, said member having an annular cavity encircling said bore, a motordisposed exteriorly of said enclosure and having the stationary partsthereof rigidly and solely mounted on said member, an annular bearingsupported on said member coaxially with said bore, a

shaft driven by said motor and journaled on said bearing to projectthrough said bore with the surface of said shaft close to but out ofrunning contact with the surface of the bore, and means for circulatinga coolant through said cavity to cool the surface of said bore and henceuniformly cool said shaft.

References Cited in the file of this patent UNITED STATES PATENTS1,727,192 Baily Sept. 3, 1929 4 Roth et al. Dec. 3, 1935 Harsch Aug. 1,1939 Rosecrans Oct. 17, 1939 Mumford Mar. 3, 1953 FOREIGN PATENTS FranceApr. 25, 1938 Great Britain July 5, 1938

